DC Comics, on its covers anyway, happily promoted the war effort after Pearl Harbor; but as Francis W. Porretto reports, they drew the line at actually having Superman siding with the Allies:
A significant number of readers demanded to know why Superman didn’t participate in the war — on the side of the Allies, of course; the editors of DC Comics replied that their superhero believed the Allies could and should win the war through their own efforts, and that he could do better service to “truth, justice, and the American way” on the home front.
How they did this was exquisite:
DC needed a plausible plot device to allow Superman, and Clark Kent, to be outside of the draft and remain in Metropolis and not enter World War II, as most men were doing. In an interesting story, Clark Kent was drafted but failed his induction eye-exam, and was declared 4-F (undraftable) when he accidentally used his x-ray vision and read the eye chart in the next room. With this “error”, Kent and Superman were free to work “from the outside” to affect the war.
And it’s just as well. FWP again:
It gave me a chuckle even back then. A comic-book character is supposed to participate in a real-world war? Suppose the war didn’t eventuate as the comics would have it? What would that have done to the franchise? C’mon, boys and girls: this is just cheap, colorful, escapist entertainment!
Believe me, I know the perils of writing too much reality, to the extent that “reality” is definable in the My Little Pony universe, into such a matter: those of us who have toiled over real-time Twilight Sparkle stories were thrown for a cosmic loop at the end of the third season, when Twi, having resolved an Ancient Mystery, is unexpectedly promoted to royalty, and we were essentially given the option of adjusting our narratives accordingly or declaring the Alternate Universe tag in play. I chose the former, and it has complicated my life, or at least my story, immensely.